Research Methodology - Dr. Krishan K. Pandey

42 Research Methodology
Test area:
Control area:
Fig. 3.2
The basic assumption in such a design is that the two areas are identical with respect to their
behaviour towards the phenomenon considered. If this assumption is not true, there is the possibility
of extraneous variation entering into the treatment effect. However, data can be collected in such a
design without the introduction of problems with the passage of time. In this respect the design is
superior to before-and-after without control design.
3. Before-and-after with control design: In this design two areas are selected and the dependent
variable is measured in both the areas for an identical time-period before the treatment. The treatment
is then introduced into the test area only, and the dependent variable is measured in both for an
identical time-period after the introduction of the treatment. The treatment effect is determined by
subtracting the change in the dependent variable in the control area from the change in the dependent
variable in test area. This design can be shown in this way:
Test area:
Control area:
Treatment introduced
Treatment Effect = (Y) – (Z)
Level of phenomenon
before treatment (X)
Fig. 3.3
This design is superior to the above two designs for the simple reason that it avoids extraneous
variation resulting both from the passage of time and from non-comparability of the test and control
areas. But at times, due to lack of historical data, time or a comparable control area, we should prefer
to select one of the first two informal designs stated above.
4. Completely randomized design (C.R. design): Involves only two principles viz., the principle
of replication and the principle of randomization of experimental designs. It is the simplest possible
design and its procedure of analysis is also easier. The essential characteristic of the design is that
subjects are randomly assigned to experimental treatments (or vice-versa). For instance, if we have
10 subjects and if we wish to test 5 under treatment A and 5 under treatment B, the randomization
process gives every possible group of 5 subjects selected from a set of 10 an equal opportunity of
being assigned to treatment A and treatment B. One-way analysis of variance (or one-way ANOVA) *
is used to analyse such a design. Even unequal replications can also work in this design. It provides
maximum number of degrees of freedom to the error. Such a design is generally used when
experimental areas happen to be homogeneous. Technically, when all the variations due to uncontrolled
* See Chapter 11 for one-way ANOVA technique.
Treatment
introduced
Level of phenomenon
without treatment
(A)
Treatment Effect = (Y – X) – (Z – A)
Level of phenomenon after
treatment (Y)
Level of phenomenon without
treatment (Z)
Time Period I Time Period II
Level of phenomenon
after treatment (Y)
Level of phenomenon
without treatment
(Z)